I loaded the latest release the other day and performed a workout tonight. I had several intermittent drops and an extended drop that forced me to abort. I then went into the settings and turned off the automatic upload to Strava (that was the fix for the latest release), switch the USB port and started a new workout. The second workout work great, just as expected. I'm not sure if changing the USB port or turning off the Strava upload was to culprit but it seemed to be one of the two that was the problem.

I upload the .fit file to Runningahead.com which I use as my online training diary and the uploads up until the latest versions where working great. The latest release, however, doesn't seem to have the distance in the .fit file for RA to read. I get the other data, just no distance.

I haven't had any issues with the .FIT files I've created and uploaded to Training Peaks or Strava. I also haven't touched the .FIT code in a while. I would recommend trying your .FIT file on some other services to see if they read it correctly.